The present invention relates to a method and apparatus for remote sensing of mechanical force caused by a given event by generating a light signal in the vicinity of the event and then transmitting the light signal to a remote location where it can be analyzed and stored as desired. The present invention has particular but not exclusive application to the remote sensing of mechanical forces such as those created by an explosion.
Measurement of mechanical force generated in the vicinity of hazardous conditions such as are produced in the testing of explosives can be difficult and expensive. The duration of such tests is typically very short, and they normally cannot be repeated. Nevertheless, it is often necessary to record large amounts of data generated by the explosion for later analysis. Furthermore, inasmuch as there is high probability that the remote sensing apparatus will be destroyed during the test, it is desirable that the equipment be inexpensive as well as reliable.
Conventional measurement of mechanical force generated in a hazardous test is typically accomplished by devices which transform mechanical force into an electrical signal. These include piezomagnetic devices, piezoelectric devices, strain gauges, and other varieties of pressure transducers. The electrical output of these devices typically must be amplified before it is transmitted to a remote data recorder. When it is necessary to make measurements in a very hostile environment the electrical devices, cabling, and other instrumentation are frequently destroyed. These devices also have the disadvantage that reliable operation of electrical circuits and transmission of the electric signals are frequently disrupted by the very event they are intended to measure, so that the readings obtained are distorted part usefulness. For example, a phenomenon known as the "cable-squeeze" phenomenon causes the generation of spurious electrical impulses when a cable is deformed. It is difficult thereafter to discriminate between these spurious impulses and the data signals generated by the transducer.
In summary, prior art methods and apparatus which rely upon proximate generation and subsequent transmission of an electrical signal to a remote location to measure mechanical forces have not proved to be satisfactory due to unreliability, expense, and the difficulty in interpreting data acquired thereby.